1. Field of the Invention
The invention relates to a light-emitting element and, in particular, to a light-emitting element including a semiconductor substrate opaque (or not transparent) to light emitted from a light emitting portion, and a reflective portion formed between the semiconductor substrate and the light emitting portion.
2. Description of the Related Art
A conventional light-emitting element is known which includes an n-type GaAs substrate, a light reflection layer formed on the n-type GaAs substrate, an n-type Al0.45Ga0.55As cladding layer formed on the light reflection layer, a p-type GaAs active layer formed on the n-type Al0.45Ga0.55As cladding layer, a p-type Al0.45Ga0.55As cladding layer formed on the p-type GaAs active layer and a p-type GaAs cap layer formed on the p-type Al0.45Ga0.55As cladding layer, and in which the light reflection layer has a laminated structure of n-type AlAs/n-type AlxGa1-x As, the laminated structure is formed in a chirp shape with continuously varied film thickness, and a relation among a variable thickness ratio, the number of laminated layers and a mix crystal ratio is defined to obtain a predetermined reflection wavelength band and a reflectance (see, e.g., JP-A-5-37017).
Since the light reflection layer of the light-emitting element disclosed in JP-A 5-37017 reflects light traveling toward a semiconductor substrate side by optical interference, it is possible to improve the optical output.